RegExp and UTF-8 Characters

[Dan0100]

Hi everyone,
I am relatively new to Java and RegExp.
At the moment I am building a socket server where I use UTF-8 control characters (\u0000 - \u0007) for special messages.

What I am looking for is a RegExp pattern to convert all of these to a $ symbol. My main problem is actually specifying the characters in the RegExp.

This works:

myNewString = myString.replaceAll("\u0000", "$")

But this doesn't work and it is what I need:

myNewString = myString.replaceAll("[\u0000-\u0007]", "$")

Thanks for your help and reading,
Dan

[Webuser]

Hello :)

You can use code like a

char d;
void gogo(int c)
  {
   int a=(int)'\u0000';
   int b=(int)'\u0007';
   
   if(c>=a && c<=b){d='$';}
   

  }

[Norm]

I get the following error with these lines of code:
String myString = "First this \u0000 for testing";
String myNewString = myString.replaceAll("\u0000", "$"); // line 31

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 1
at java.lang.String.charAt(String.java:687)
at java.util.regex.Matcher.appendReplacement(Matcher. java:711)
at java.util.regex.Matcher.replaceAll(Matcher.java:81 3)
at java.lang.String.replaceAll(String.java:2190)
at TestStatement.main(TestStatement.java:31)

[Webuser]

Or this one...

char gogo(int c)
  {
   int a=(int)'\u0000';
   int b=(int)'\u0007';
   char d=(char)c;
   if(c>=a || c<=b){d='$';}

   System.out.println(d);
   return d;
  }

[DarrylBurke]

0.

This works:

myNewString = myString.replaceAll("\u0000", "$")

I don't think so. That code should produce the error Norm reported. Probably the code you posted isn't the code you ran. Don't do that -- it greatly reduces the chances of getting targeted help on a forum.

1. The dollar sign is a metacharacter in the replacement String and needs to be quoted with a double backslash.

2. There's no problem with the character class or the unicode characters.

myNewString = myString.replaceAll("[\u0000-\u0007]", "\\$")

db

[JosAH]

Hello :)

You can use code like a

char d;
void gogo(int c)
  {
   int a=(int)'\u0000';
   int b=(int)'\u0007';
   
   if(c>=a && c<=b){d='$';}
   

  }

Don't you people ever read the API documentation? The docs for the String.replaceAll( ... ) method clearly state:

Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceAll. Use Matcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.

So the dollar sign should be escaped, as in "\\$"

kind regards,

Jos

[Fubarable]

Don't the unicode escape sequences need to be escaped or double backslashes as well? i.e.,

public class UnicodeRegEx {
   public static void main(String[] args) {
      String test = "Hello World";
      
      System.out.println(test);
      
      String regex = "[\\u0061-\\u0079]";
      
      test = test.replaceAll(regex, "\\$");
      System.out.println(test);
   }
}

[JosAH]

Don't the unicode escape sequences need to be escaped or double backslashes as well? i.e.,

public class UnicodeRegEx {
   public static void main(String[] args) {
      String test = "Hello World";
      
      System.out.println(test);
      
      String regex = "[\\u0061-\\u0079]";
      
      test = test.replaceAll(regex, "\\$");
      System.out.println(test);
   }
}

Nope, those \uxxxx escape sequences are handled by javac, the Java compiler; the regexp compiler doesn't care about special characters in funny intervals, it just cares about its meta characters, so the regexp is:

String regex = "[\u0061-\u0079]";

kind regards,

Jos

[Fubarable]

Thank you Jos. Makes sense.

[Dan0100]

Thanks for all the replies everyone!
Oh no I was so unlucky to choose the $ dollar symbol lol.

Ok so all I needed was to add the \\$ instead of $ and it works perfectly now, thank you very much guys.

Working code:

msg.replaceAll("[\u0000-\u0007]", "\\$");

Norm + Darryl.Burke, I understand now that the code I ran SHOULDN'T have worked but for some reason it honestly DID work on my compiler.

JosAH, I did read the documentation A LOT and I can't find anything about $ symbols here: String (Java 2 Platform SE v1.4.2))

Thanks again everyone!

[JosAH]

JosAH, I did read the documentation A LOT and I can't find anything about $ symbols here: String (Java 2 Platform SE v1.4.2))

I even copied/pasted the relevant parts of the docs for you (see reply #6). b.t.w. Java 1.4.2. is dead, you should update your jvm and the documentation.

kind regards,

Jos

[Dan0100]

Oh Ok. Java SE 6, sorry, but but google says... lol!
Thanks.